Nice work, did you follow any guides or tutorials? I am also in the process of writing a similar script and found a few guides along with #bash on freenode.

Try using 'esc' at startup, not 'F2', then select the sd card. It worked on my 900. Message me if you need more help.

Coincidentally, I am using an 8GB SD card as well.

I had to use this method (esc, not BIOS settings) to boot my SD card.